JP2017002324A - Sidewall for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a resistance to carving of a tire sidewall without adversely affecting good crack resistance performance and low rolling resistance performance.SOLUTION: The tire sidewall has at least a part including a rubber composition comprising as a base at least a diene elastomer, a crosslinking system and a filler for reinforcement. The content of the filler for reinforcement in the composition varies in the range of 20 to 40 phr (pts.mass per 100 mass of elastomer), the volume fraction of the filler for reinforcement in the composition is in the range of 8.0% to 13.0% and the filler for reinforcement mainly includes carbon black or a mixture of carbon black each having a BET specific surface area in the range of 50 m/g to 69 m/g.SELECTED DRAWING: None

Description

  The present invention relates to a tire having a side wall based on a rubber composition, and more particularly to a tire intended to be mounted on a passenger car.

The tire typically includes two beads intended to contact the rim, a crown composed of at least one crown reinforcement and a tread, and two sidewalls, the tire being carcass reinforcement secured within the two beads. It is reinforced with materials.
The sidewall is an elastomeric layer disposed between the crown and the bead on the outside of the carcass reinforcement relative to the internal cavity of the tire and completely or partially covering the area of the carcass reinforcement extending from the crown to the bead.

  Tire sidewalls, particularly tire sidewalls of vehicles operating in urban environments, are subject to wear resulting from friction against paved roads. This phenomenon is also referred to as carving and has the effect of abrading the outer surface of the sidewall. This wear can lead to deterioration that renders the tire unusable. In particular, the carcass reinforcement must not be deteriorated. This is why the sidewalls must be sufficiently resistant to carving wear in order to protect the carcass reinforcement from physical stress such as carving or chemical stress such as ozone. In improving this abrasion resistance, those skilled in the art generally rely on the use of rubber compositions containing relatively high contents of reinforcing fillers.

  In view of the deformation period such as bending experienced by the sidewall, the composition must have the lowest possible hysteresis and be sufficiently flexible in order to be usable as the sidewall. The person skilled in the art is aware that he is facing the problem of reconciling the low rolling resistance and flexibility of the sidewalls. However, while the introduction of a high content of reinforcing filler is necessary to improve the resistance to carving, as can be seen above, it increases the rolling resistance and makes the composition possible. Has the result of reducing flexibility.

Furthermore, the bending periods experienced by the sidewalls when the tire rotates, especially when these periods combine the action of ozone, cause cracks or cracks, especially in the sidewalls, and the tires are independent of tread wear. Can interfere with the use of.
Accordingly, those skilled in the art must find a solution to improve the resistance to sidewall carving without adversely affecting the low rolling resistance and good crack resistance performance.

  As described in many references (among these references, references EP 1 462 479 B1, EP 1 975 200 A1, EP 1 033 265 B1, EP 1 357 149 A2, EP 1 231 080 A1 and US Pat. No. 4,824,900), commonly used compositions for side walls are based on natural rubber and synthetic rubbers such as polybutadiene and carbon black.

For passenger cars, it is known to those skilled in the art to use carbon black with a BET specific surface area, more preferably strictly lower than 49 m ² / g. For heavy goods vehicles, carbon black with a BET specific surface area between 70 m ² / g and 99 m ² / g is usually used. The proportion of carbon black introduced into the side wall is customarily around 50 phr (parts per 100 parts by weight of elastomer) with a volume fraction of at least 15%, both for passenger cars and for heavy goods vehicles; The volume fraction corresponds to the volume of carbon black relative to the volume of all components of the composition, as defined in more detail in paragraph I-1 below.

The Applicant has, surprisingly, a mixture of carbon black or carbon black having a BET specific surface area in the range of 50m ² / g~69m ² / g, as the main reinforcing filler in the sidewall rubber composition, 50 phr Use with a reinforcing filler volume fraction that is much lower than the reinforcing filler content and much lower than 15%, which makes the side wall carving resistance, good crack resistance performance and low rolling It has been found that it is possible to improve without adversely affecting the resistance performance or even to improve one of these two properties.

The present invention is a tire sidewall comprising at least a portion thereof a rubber composition based on at least a diene elastomer, a crosslinking system and a reinforcing filler, wherein the content of the reinforcing filler in the composition is Varying from 20 to 40 phr, the volume fraction of reinforcing filler in the composition is in the range of 8.0% to 13.0%, and this reinforcing filler is mainly from 50 m ² / g to 69 m ² / It relates to a tire sidewall characterized in that it comprises carbon black or a mixture of carbon blacks having a BET specific surface area in the range of g.

Another subject of the invention is a tire sidewall composition based on at least a diene elastomer, a crosslinking system and a reinforcing filler, wherein the reinforcing filler content in the composition is 20-40 phr. fluctuated, the volume fraction of the reinforcing filler in the composition is in the range of 8.0% to 13.0%, and the reinforcing filler is mainly in the range of 50m ² / g~69m ² / g A tire sidewall composition comprising carbon black or a mixture of carbon blacks having a certain BET specific surface area, comprising the following steps:
Kneading the diene elastomer and the reinforcing filler thermomechanically until a maximum temperature between 110 ° C. and 190 ° C. is reached;
Cooling the mixture to a temperature below 100 ° C .;
-Then, the process of mixing the said crosslinking system;
-Kneading everything until a maximum temperature lower than 110 ° C is reached to obtain a rubber composition;
A step of calendering or extruding the rubber composition.

The present invention also provides a tire sidewall including a rubber composition based at least in part on a diene elastomer, a crosslinking system, and a reinforcing filler, the reinforcing filler being contained in the composition. The amount varies between 20 and 40 phr, the volume fraction of reinforcing filler in the composition is in the range of 8.0% to 13.0%, and this reinforcing filler is mainly 50 m ² / g to 69 m It also relates to a tire comprising said tire sidewall, characterized in that it comprises carbon black or a mixture of carbon blacks having a BET specific surface area in the range of ² / g.
Advantageously, the tire according to the invention is intended to be mounted on a heavy-duty vehicle or a passenger car, more preferably a passenger car.

I. Measurements and Test Methods Used The rubber compositions or sidewalls containing these rubber compositions are characterized after curing, as shown below.

I-1. Volume fraction of reinforcing filler The volume fraction of reinforcing filler in a rubber composition is defined as the ratio of the volume of reinforcing filler to the volume of all components of the composition. It is to be understood that the volume of all components is calculated by summing the volume of each component of the composition. Accordingly, the volume fraction of reinforcing filler in the composition is defined as the volume ratio of reinforcing filler to the sum of the respective component volumes of the composition.

I-2. Rolling resistance performance The dynamic characteristic tan δ _max is measured in a viscosity analyzer (Metravib VA4000) according to ASTM D 5992-96 standard. Sample of vulcanized composition subjected to simple alternating sinusoidal shear stress at a frequency of 10 Hz and under standard temperature conditions (23 ° C.) according to ASTM D 1349-09 standard (having a cross-sectional area of ² mm thickness and 79 mm ² Record the response of the cylindrical test specimen). Inter-vertex strain amplitude sweeps are performed from 0.1% to 50% (outward cycle) and then from 50% to 0.1% (return cycle). The result collected is the loss factor tanδ. In the return cycle, the highest observed tan δ (tan δ _max ) is shown.
The figure of merit is the ratio of the tan δ _max value of the control composition to the tan δ _max value of the study example. Since the control has an index of 100, a value higher than 100 indicates good rolling resistance performance.

I-3. Manufacture a tire with a crack performance size of 205 / 55R16 and rotate it on a flywheel at 70 km / hr; the side wall of this tire first has a crack with a length of 20 mm and a depth of 1.7 mm Cut in. The test is discontinued after 25000 km or when a pressure drop is observed.
The figure of merit is the ratio of the length propagated at the surface of the control tire to the length propagated at the surface of the measured tire. Since the control has an index of 100, values higher than 100 indicate good crack resistance performance.

I-4. Sidewall carving performance This test is carried out on a vehicle, and its left front tire rubs the paved road with slow motion. The test is discontinued when the carcass ply cord appears or when a pressure drop is observed. The result provided is the mass loss of the tire per mileage. The figure of merit is the ratio of the mass loss per mileage of the control to the mass loss per mileage of the study example. Since the control has an index of 100, a value higher than 100 indicates good carving resistance performance.

II. Detailed Description of the Invention In the present description, all percentages (%) are by weight unless otherwise specified. Furthermore, the interval between the values indicated by the expression “between a and b” indicates a range of values ranging from greater than a to less than b (ie excluding limit values a and b). On the other hand, the interval between the values indicated by the expression “a to b” means a range of values ranging from a to b (that is, including strict limit values a and b).

The side wall according to the invention is composed of at least one part comprising a rubber composition based on at least one diene elastomer, a crosslinking system and a reinforcing filler, the content of reinforcing filler in the composition being Varying from 20 to 40 phr, the volume fraction of reinforcing filler in the composition is in the range of 8.0% to 13.0%, and this reinforcing filler is mainly from 50 m ² / g to 69 m ² / It has the essential feature that it is characterized by comprising carbon black or a mixture of carbon blacks with a BET specific surface area in the range of g.

According to one preferred embodiment, this part of the side wall is placed on the outer surface of the side wall.
According to another preferred embodiment, this part of the sidewall extends from the crown to the bead.
According to another preferred embodiment, this part of the side wall comprising the composition according to the invention may be in the form of a shape element applied to the side wall region which has a tendency to rub the paved road.

Where appropriate, other optional components of the sidewalls may be based on different rubber compositions known to those skilled in the art, such as carbon black N550 or N660 (at least in a 15.0% filler volume fraction). Based on ASTM D1765-06 standard).
II-1. Diene Elastomer The term “diene” elastomer or rubber, as is known, is a diene monomer (a monomer bearing two carbon-carbon double bonds that may be conjugated or non-conjugated). ) Is meant to mean one or more elastomers (ie homopolymers or copolymers) derived at least in part.

  These diene elastomers can be divided into two categories: “essentially unsaturated” or “essentially saturated”. The expression “essentially unsaturated” generally means a diene elastomer derived at least in part from a conjugated diene monomer having a diene origin (conjugated diene) unit content greater than 15% (mol%). I want you to understand. Thus, diene elastomers, such as butyl rubber or EPDM type diene / α-olefin copolymers, do not fall within the above definition, and in particular are “essentially saturated” diene elastomers (low or very low diene which is always less than 15%). Origin unit content). In the category of “essentially unsaturated” diene elastomers, the expression “highly unsaturated” diene elastomers especially means diene elastomers having a unit content of more than 50% of diene origin (conjugated dienes). I want to be understood.

In view of these definitions, the diene elastomers that can be used in the present invention are to be understood in more detail as meaning:
(a) any homopolymer obtained by polymerizing conjugated diene monomers containing 4 to 12 carbon atoms;
(b) any copolymer obtained by copolymerizing one or more conjugated dienes with another diene or one or more vinyl aromatic compounds containing from 8 to 20 carbon atoms;
(c) 3-6 ethylene and propylene and non-conjugated diene monomers of the following types, in particular ethylene, such as elastomers obtained from, for example, 1,4-hexadiene, ethylidene norbornene or dicyclopentadiene Three-component copolymers obtained by copolymerizing α-olefins containing 5 to 12 carbon atoms with non-conjugated diene monomers containing 6 to 12 carbon atoms;
(d) Copolymers of isobutene and isoprene (butyl rubber), and also halogenated forms, in particular chlorinated or brominated forms, of this type of copolymer.

  Although the present invention applies to any type of diene elastomer, those skilled in the tire art will preferably use the present invention in particular for the above-described type (a) or (b) essentially unsaturated diene elastomer. It should be understood that it is intended for use with.

The following are particularly suitable as conjugated dienes: 1,3-butadiene; 2-methyl-1,3-butadiene; for example 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3 2,3-di (C ₁ -C ₅ alkyl) -1,3 such as -butadiene, 2-methyl-3-ethyl-1,3-butadiene or 2-methyl-3-isopropyl-1,3-butadiene -Butadiene; aryl-1,3-butadiene, 1,3-pentadiene or 2,4-hexadiene. The following are suitable, for example, as vinyl aromatics: styrene; ortho-, meta- and para-methylstyrene; “vinyl-toluene” commercial mixtures; para- (tert-butyl) styrene; methoxystyrene; chlorostyrene; Vinyl mesitylene; divinyl benzene or vinyl naphthalene.
The copolymer may contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinyl aromatic units.

  The elastomer may have any microstructure depending on the polymerization conditions used, in particular the presence or absence of modifiers and / or randomizers and the amount of modifier and / or randomizer used. The elastomers can be, for example, block, random, ordered or fine ordered elastomers and can be prepared in dispersion or in solution; these elastomers can be coupling agents and / or star branching agents or functional groups. It can be coupled and / or star-branched or functionalized with an agent. Coupling with carbon black can include, for example, a functional group containing a C-Sn bond, or an amino functional group such as aminobenzophenone; coupling to a reinforcing inorganic filler such as silica Include, for example, silanol or polysiloxane functional groups having silanol ends (e.g. as described in FR 2 740 778 or US 6 013 718), alkoxysilane groups (e.g. FR 2 765 882 or As described in US 5 977 238), carboxyl groups (e.g. as described in WO 01/92402 or US 6 815 473, WO 2004/096865 or US 2006/0089445) Or polyether groups (for example as described in EP 1 127 909 or US 6 503 973). Other examples of functionalized elastomers may also include epoxidized type elastomers (such as SBR, BR, NR or IR).

The following are suitable: polybutadiene, especially polybudiene having a 1,2-unit content (mol%) between 4% and 80% or a cis-1,4-unit content (mol%) greater than 80% Polybutadiene with styrene; polybutadiene, styrene copolymer, in particular T _g between 0 ° C. and −70 ° C., in particular between −10 ° C. and −60 ° C. (glass transition temperature Tg, measured according to standard ASTM D3418), 5 Styrene content between 20% and 60% by weight, in particular between 20% and 50% by weight, butadiene component 1,2-bond content (mol%) and 10% between 4% and 75%. Copolymers with trans-1,4-bond content (mol%) between 80%; butadiene / isoprene copolymers, in particular isoprene content between 5% and 90% and -40 ° C to -80 ° C copolymers having a T _g; or, isoprene / styrene copolymers, in particular, of 5 wt% and 50 wt% Copolymer having a T _g between the styrene content and -25 ° C. and -50 ° C.. In the case of butadiene / styrene / isoprene copolymers, a styrene content of between 5 and 50% by weight, in particular between 10 and 40% by weight, between 15 and 60% by weight, in particular 20% by weight Isoprene content between 50% by weight, butadiene content between 5% and 50% by weight, especially between 20% and 40% by weight, 1,2-unit of butadiene component between 4% and 85% Content (mol%), butadiene component trans-1,4-unit content between 6% and 80% (mol%), Isoprene component 1,2- + 3,4-unit between 5% and 70% A copolymer having a content (mol%) and an isoprene component trans-1,4-unit content (mol%) between 10% and 50%, more generally between −20 ° C. and −70 ° C. Any butadiene / styrene / isoprene copolymer having a T _g is particularly suitable.

  Preferably, the diene elastomer used in the present invention is a polybutadiene (abbreviated as “BR”), synthetic polyisoprene (IR), natural rubber (NR), butadiene copolymer, isoprene copolymer and mixtures of these elastomers. Selected from the group of saturated diene elastomers. Such copolymers are more preferably selected from the group consisting of butadiene / styrene copolymers (SBR), isoprene / butadiene copolymers (BIR), isoprene / styrene copolymers (SIR) and isoprene / butadiene / styrene copolymers (SBIR).

  The rubber composition according to the present invention may contain a single diene elastomer or a mixture of several diene elastomers; the diene elastomer (s) may be any type of synthetic elastomer other than diene elastomers, or other than elastomers Can be used in combination with other polymers, such as even thermoplastic polymers.

  According to one particular embodiment, the rubber composition comprises at least one essentially saturated diene elastomer, in particular at least one EPDM copolymer or butyl rubber (chlorinated or brominated as required). These copolymers are used alone or as a blend with a highly unsaturated diene elastomer as described above, in particular NR or IR, BR or SBR.

  According to one preferred embodiment, the diene elastomer in the composition comprises 30-55% natural rubber, synthetic polyisoprene or a mixture of natural rubber and synthetic polyisoprene, 45-70% polybutadiene, styrene. Elastomer mixtures consisting of diene elastomers selected from / butadiene copolymers, isoprene / butadiene copolymers, isoprene / styrene copolymers and isoprene / butadiene / styrene terpolymers and mixtures thereof are used.

  The synthetic polyisoprene is preferably a synthetic cis-1,4-polyisoprene; preferably a poly having a cis-1,4-bond content (mol%) of greater than 90%, preferably greater than 98%. Isoprene.

  According to one more preferred embodiment, 30 to 55% natural rubber, synthetic polyisoprene or a mixture of natural rubber and synthetic polyisoprene and 45 to 70% polybutadiene, preferably cis-1,4-polybutadiene, That is, a mixture of polybutadiene having a cis-1,4-bond content of more than 90% (mol%), preferably 96% (mol%) or more is used.

  Advantageously, the polybutadiene is coupled with a coupling agent and / or a star branching or functionalizing agent and / or a star for coupling to carbon black or silica as described above. Can be branched or functionalized. Also, the functionalization of the polybutadiene can be carried out in the step of initiating the butadiene polymerization reaction using, for example, a functional initiator such as an organolithium, lithium amide or organotin lithium compound bearing an amine functional group. .

II-2. Reinforcing filler said reinforcing filler, organic filler, carbon of at least one having a BET specific surface area in the range of 50m ² / g~69m ² / g (i.e., one or more) Including black. These carbon blacks are, for example, SR401 blacks from Sid Richardson and Spheron 1416 blacks from Cabot. These carbon blacks may already be incorporated into the isoprene elastomer, for example in the form of a masterbatch (see, for example, application WO 97/36724 or WO 99/16600).
It is explained that the BET specific surface area was measured according to the ASTM D6556-09 standard [multi-point (5-point) method (gas: nitrogen; relative pressure range: P / P0: 0.05 to 0.30)].

Also, suitable as carbon black, carbon black mixture of carbon black mixture is characterized by having a BET specific surface area in the range of 50m ² / g~69m ² / g.
In particular, the carbon black constituting such a mixture is various ASTM grade carbon blacks.

The essential feature of the present invention, in the rubber composition mainly containing a reinforcing filling 20~40phr carbon black or carbon black mixtures having a BET specific surface area in the range of 50m ² / g~69m ² / g The volume fraction of the reinforcing filler in the composition is in the range of 8.0% to 13.0%. The term "primarily", carbon black or carbon black mixtures having a BET specific surface area in the range of 50m ² / g~69m ² / g is meant to indicate more than 50% by weight of reinforcing filler.

Reinforcing filler 20～40Phr (as already mentioned, mainly, carbon black or carbon black mixtures having a BET specific surface area in the range of 50m ² / g~69m ² / g) and 8.0 to 13.0% This double condition for the range of volume fractions is essential to satisfy the above-mentioned problems. Surprisingly,
Depending on the volume fraction of this reinforcing filler higher than 13.0% with more than 40 phr reinforcing filler, the composition may be too hysteretic and too stiff for use as a tire sidewall become;
Depending on the volume fraction of this reinforcing filler between 8.0% and 13.0% with more than 40 phr reinforcing filler, the content of diene elastomer in the composition is sufficient for the composition Too low to secure;
For reinforcing fillers less than 20 phr, the amount of reinforcing filler is small to allow sufficient reinforcing power of the sidewall composition, regardless of the volume fraction of this reinforcing filler. Pass;
A volume fraction of reinforcing filler lower than 8.0% corresponds to filler dilution that is too high, regardless of reinforcing filler content, resulting in reduced carving wear;
A range corresponding to a reinforcing filler content between 20 phr and 40 phr with a volume fraction of this reinforcing filler higher than 13.0% is to obtain a composition having the desired compromise of properties. Not possible. In fact, at the lowest reinforcing filler content within this range (i.e., near the lower limit), it is impossible to achieve a reinforcing filler volume fraction higher than 13.0%, and At the highest content in this range, the composition is too hysteretic and / or too rigid for use as a tire sidewall.

Said reinforcing filler is mainly because of carbon black or carbon black mixtures having a BET specific surface area in the range of 50m ² / g~69m ² / g, the reinforcing filler, a small amount, one Other reinforcing fillers as described above may be included. Reinforcing organic fillers and reinforcing inorganic fillers are suitable as other reinforcing fillers.

The 50m ² / g~69m reinforcing organic filler other than carbon black or carbon black mixtures having a BET specific surface area in the range of ² / g, for example, 50 m ² / g such as carbon black N683 or carbon black N550 And carbon blacks having a BET specific surface area strictly lower than 69 m ² / g such as carbon black N110 or carbon black N299.
Also suitable as reinforcing organic fillers are functionalized polyvinyl aromatic organic fillers as described in applications WO-A-2006 / 069792 and WO-A-2006 / 069793.

  The expression “reinforcing inorganic filler” is defined in this patent application as “white filler”, “transparent filler” or even “non-black filler” as opposed to carbon black, by definition. It is also known, and can itself reinforce a rubber composition intended for the manufacture of tires without any means other than intermediate coupling agents, in other words normal tire grade carbon black and its reinforcing function Should be understood to mean any inorganic or mineral filler that can be substituted in (regardless of its color and its origin (natural or synthetic)); such fillers are generally known It is characterized by the presence of hydroxyl (—OH) groups on its surface.

  The physical state of supplying the reinforcing inorganic filler is not critical, whether in the form of powder, microbeads, granules, beads or any other suitable dense form. Of course, the expression “reinforcing inorganic filler” is also understood to mean a mixture of various reinforcing inorganic fillers, in particular highly dispersible siliceous and / or alumina fillers as described below. I want.

Siliceous type mineral fillers, in particular silica (SiO ₂ ), or alumina type mineral fillers, in particular alumina (Al ₂ O ₃ ), are particularly suitable as reinforcing inorganic fillers. The silica used may be any reinforcing silica known to those skilled in the art, in particular, both 450m less than ² / g, preferably any precipitated or pyrogenic silica having a BET surface area and a CTAB specific surface area is 30 to 400 m ² / g possible. Highly dispersible precipitated silica ("HDS") includes, for example, Ultrasil 7000 and Ultrasil 7005 silicas from Degussa; Zeosil 1165MP, 1135MP and 1115MP silicas from Rhodia; Hi-Sil EZ150G silica from PPG; Zeopol 8715, 8745 or 8755 silica from Huber; or silicas having a high specific surface area as described in application WO 03/16837.

  In order to couple the reinforcing inorganic filler to the diene elastomer, it is known to provide a satisfactory bond of chemical and / or physical properties between the inorganic filler (its particle surface) and the diene elastomer. At least difunctional coupling agents (or binders) intended to be used, in particular bifunctional organosilanes or polyorganosiloxanes.

Ratio of 50m ² / g~69m reinforcing filler other than carbon black or carbon black mixtures having a BET specific surface area in the range of ² / g, depending on the BET specific surface area, also compromise the desired performance Adjust according to. Thus, for example, using carbon black with a BET specific surface area strictly higher than 69m ² / g optimizes the wear resistance and minimizes the amount carefully to adversely affect the rolling resistance. It is possible to avoid it. Also, for example, use a carbon black having a BET specific surface area strictly lower than 50 m ² / g, which is preferred for optimizing low rolling resistance performance, as a small reinforcing filler in the composition according to the present invention. Is also possible.

According to one preferred embodiment, carbon black or carbon black mixtures having a BET specific surface area in the range of 50m ² / g~69m ² / g constitutes at least 85% by weight of reinforcing filler. Even more preferably, carbon black or carbon black mixtures having a BET specific surface area in the range of 50m ² / g~69m ² / g constitutes at least 95% by weight of reinforcing filler. Advantageously, the carbon black or carbon black mixtures having a BET specific surface area in the range of 50m ² / g~69m ² / g is exclusively used as a reinforcing filler, i.e., 50m ² / g~69m ² / g Carbon black or carbon black mixture having a BET specific surface area in the range of 100% constitutes 100% of the reinforcing filler.

  According to another preferred embodiment, the proportion of reinforcing filler in the rubber composition varies from 20 to 35 phr, more advantageously from 25 phr to 30 phr. When the reinforcing filler is used preferably in a proportion ranging from 20 phr to 35 phr, more preferably from 25 phr to 30 phr, the volume fraction of the reinforcing filler is preferably 8.0% to 10.0%, more preferably 8.7% to It varies from 9.4%, even more preferably from 8.9% to 9.2%. These preferred ranges for reinforcing filler content and volume fraction are that compositions with reinforcing filler content and volume fraction comply with these preferred ranges enhance carving resistance and low rolling resistance performance. And as long as it improves good crack resistance performance, it is a preferred embodiment that makes it possible to optimize the compromise between rolling resistance performance, crack resistance performance and carving resistance performance.

According to another embodiment, the carbon black or carbon black mixtures having a BET specific surface area in the range of 50m ² / g~69m ² / g are, COAN absorption value in a range of 80ml / 100g~120ml / 100g Have Values in this range of the COAN number are advantageous for imparting better properties to the sidewall rubber composition. In fact, a carbon black or carbon black mixture having a COAN number lower than 120 ml / 100 g stiffens the sidewall rubber composition lower than a carbon black having a COAN number higher than 120 ml / 100 g; whereas 80 ml / 100 g The use of a carbon black or carbon black mixture having a higher COAN number makes it possible to achieve a good dispersion of the carbon black or the carbon black mixture in the sidewall rubber composition. It is explained that the COAN number is measured according to the ASTM D3493-09 standard.

II-3. Crosslinking Systems Crosslinking systems are preferably based on vulcanization systems, ie sulfur (or sulfur donor) and primary vulcanization accelerator. In this vulcanization system, various known secondary vulcanization accelerators or vulcanization activators, such as zinc oxide, stearic acid or equivalent compounds, or guanidine derivatives (particularly diphenylguanidine) are further described. Contamination during the first non-production stage and / or during the production stage.
Sulfur is preferably used at a preferred content between 0.5 phr and 12 phr, in particular between 1 phr and 10 phr, preferably between 1 phr and 3 phr. The primary vulcanization accelerator is preferably used in a content between 0.5 phr and 10 phr, preferably between 0.5 phr and 5.0 phr, more preferably between 0.5 phr and 3 phr.

  As (primary or secondary) accelerators, any compound that can act as a vulcanization accelerator for diene elastomers in the presence of sulfur, in particular thiazole type accelerators and derivatives thereof, thiuram and zinc dithiocarbamate type accelerators. Agents can be used. These accelerators include, for example, 2-mercaptobenzothiazyl disulfide (abbreviated as “MBTS”), 20-tetrabenzylthiuram disulfide (“TBZTD”), N-cyclohexyl-2-benzothiazylsulfenamide (“ CBS ”), N, N-dicyclohexyl-2-benzothiazylsulfenamide (“ DCBS ”), N-tert-butyl-2-benzothiazylsulfenamide (“ TBBS ”), N-tert-butyl- It is selected from the group consisting of 2-benzothiazylsulfenimide (“TBSI”), zinc dibenzyldithiocarbamate (“ZBEC”) and mixtures of these compounds.

II-4. Various Additives Also, according to the present invention, the rubber composition comprises, for example, a plasticizer, preferably a non-aromatic or very slightly aromatic plasticizer, such as a naphthenic oil or Paraffinic oil, MES oil or TDAE oil, glycerin esters (especially trioleate), especially natural esters such as rapeseed or sunflower vegetable oils; pigments; protective agents such as antiozonants, antioxidants; antifatigue agents; Or it may also contain all or several of the standard additives conventionally used in elastomer compositions intended for the manufacture of tires or semi-finished products for tires, such as anti-reversion agents.

  Among the antioxidants, for example, N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine (well known by the abbreviation "6-PPD"), N-isopropyl-N'-phenyl -P-phenylenediamine (abbreviated as "I-PPD"), phenylcyclohexyl-p-phenylenediamine, N, N'-di (1,4-dimethylpentyl-p-phenylenediamine, N, N'-diaryl- p-phenylenediamine (“DTPD”), diaryl-p-phenylenediamine (“DAPD”), 2,4,6-tris- (N-1,4-dimethylpentyl-p-phenylenediamino) -1,3, Mention may be made of derivatives of para-phenylenediamine (also abbreviated as “PPD” or “PPDA”), also known as substituted para-phenylenediamines, such as 5-triazines and mixtures of such diamines. For example, 1,2- Mention may also be made of quinoline derivatives (“TMQ”) such as hydro-2,2,4-trimethylquinoline, 5 and 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline, for example Substituted diphenylamines or triphenylamines as described in applications WO 2007/121936 and WO 2008/055683, in particular 4,4′-bis (1,4-isopropylamino) triphenylamine, 4,4 ′ There may also be mentioned -bis (1,3-dimethylbutylamino) triphenylamine, 4,4'-bis (1,4-dimethylpentylamino) triphenylamine, preferably the antioxidant is substituted p- Selected from the group consisting of phenylenediamine, substituted diphenylamine, substituted triphenylamine, quinoline derivatives and mixtures of such compounds.

  According to one preferred embodiment, the rubber composition according to the invention comprises a plasticizer selected from naphthenic or paraffinic oil, MES oil or TDAE oil or mixtures thereof.

  In addition to the coupling agent, the above composition comprises a coupling activator; an agent for coating an inorganic filler; and, as is known, improved dispersibility of the filler in the rubber matrix. More general processing aids can also be included that can improve the ability of the composition to be processed in the uncured state by reducing the viscosity of the product; these agents include, for example, alkylalkoxysilanes Polyols; polyethers; primary, secondary or tertiary amines; hydroxylated or hydrolysable polyorganosiloxanes.

II-5. Production of rubber composition The rubber composition is prepared in a suitable mixer in two successive production stages well known to those skilled in the art: between 110 ° C and 190 ° C, preferably 130 ° C and 180 ° C. A first stage (also referred to as a “non-production” stage) that is thermomechanically processed or kneaded at a high temperature up to a maximum temperature between, and subsequently, typically lower than 110 ° C., eg 40 ° C. Manufactured using a second stage (also referred to as “production” stage) that is machined to lower temperatures between 100 ° C .; in its finishing stage, the crosslinking system is incorporated.

A tire sidewall composition based on at least a diene elastomer, a crosslinking system and a reinforcing filler, wherein the reinforcing filler content in the composition varies between 20 and 40 phr, and the reinforcement in the composition the volume fraction of the use filler is in the range of 8.0% to 13.0%, and the reinforcing filler is mainly carbon black or having a BET specific surface area in the range of 50m ² / g~69m ² / g A process according to the present invention characterized in that it comprises the following steps of a tire sidewall composition comprising a mixture of carbon black:
Kneading the diene elastomer and the reinforcing filler thermomechanically until a maximum temperature between 110 ° C. and 190 ° C. is reached;
Cooling the mixture to a temperature below 100 ° C .;
-Then, the process of mixing the said crosslinking system;
-Kneading everything until a maximum temperature lower than 110 ° C is reached to obtain a rubber composition;
A step of calendering or extruding the rubber composition.

The first kneading step is generally carried out by mixing the reinforcing filler into the elastomer by kneading thermomechanically in one or more steps. The reinforcing filler, particularly, 50m ² / g~69m the carbon black or carbon black mixtures having a BET specific surface area in the range of ² / g is, for example, as described in patent application WO 97/36724 and WO 99/16600 If it is already fully or partially mixed in the elastomer in the form of a masterbatch, it is the masterbatch that is kneaded directly, and if appropriate, not in the form of a masterbatch Incorporate other elastomers or reinforcing fillers present in the composition.

According to one preferred embodiment of the method, the carbon black or carbon black mixtures having a BET specific surface area in the range of 50m ² / g~69m ² / g is at least 85% by weight of reinforcing filler, preferably Constitutes at least 95% by weight, even more preferably 100% by weight.
According to another preferred embodiment of the above method, the proportion of reinforcing filler varies from 20 phr to 35 phr, preferably from 25 phr to 30 phr.

According to another preferred embodiment of the above method, the volume fraction of reinforcing filler varies from 8.0% to 10.0%, preferably from 8.7 to 9.4%.
The first two steps may be performed alternately using the same mixer, or may be separated by a step of cooling to a temperature lower than 100 ° C., in which case the final step is the second step Perform using a mixer.

  For example, the first stage is performed in a single thermomechanical process, during which all essential base components (total or 1 part diene elastomer, total or 1 part reinforcing filler, and optionally A suitable coupling agent) is first introduced into a suitable mixer, such as a standard closed mixer, and then, for example after kneading for 1-2 minutes, the remaining elastomer and reinforcing fillers as appropriate, Introduce other additives excluding cross-linking systems, optional coatings or complementary processing aids. After cooling the mixture so obtained, the crosslinking system is introduced into an open mixer (eg open mill) maintained at a low temperature (eg between 40 ° C. and 100 ° C.). All ingredients are then mixed for a few minutes, for example between 2 and 15 minutes.

  The final composition thus obtained can then be calendered, for example in the form of a sheet or slab, for example for laboratory characterization, or extruded, for example as a sidewall layer. To form a rubber-shaped element used to produce a semi-finished product

Crosslinking (or curing), if appropriate vulcanization, as is known, generally depends on the temperature between 130 ° C and 200 ° C, in particular on the curing temperature, the crosslinking system used and the crosslinking rate of the composition. For example, it is carried out for a sufficient time that can vary between 5 and 90 minutes.
The following examples illustrate the invention but do not limit the invention.

III. Embodiments of the invention
III-1. Manufacture of rubber composition The following test is carried out in the following way: in a closed mixer with 70% fill and an initial vessel temperature of approximately 90 ° C, diene elastomer (mixture of NR and BR) and above The carbon black is then kneaded for 1 to 2 minutes, and then various other components excluding the vulcanization system, such as an antioxidant, an ozone degradation inhibitor, and a vulcanization activator are introduced. Thereafter, thermomechanical processing (non-production stage) is carried out in one step until a maximum “fall” temperature of approximately 165 ° C. is reached (total kneading time equal to approximately 5 minutes). The mixture so obtained is recovered and cooled, after which the vulcanization system (sulfur and sulfenamide accelerator) is added in a 70 ° C. open mixer (homo finisher) and all components are added to about 5%. Mix for ~ 6 minutes (production stage).

  The composition so obtained is then calendered into the form of a rubber slab (2-3 mm thick) or thin sheet for the measurement of its physical or mechanical properties, or the desired dimensions After cutting and / or assembling, it is extruded into a shape element that can be used directly to obtain the sidewall.

III-2. Test The purpose of this test is to demonstrate improvements in the properties of the tire sidewall according to the present invention compared to the reference tire sidewall for passenger cars. The tests, the composition, although containing a carbon black having a specific surface area in the range of 50m ² / g~69m ² / g, obey the reinforcing filler content or the invention not according to the invention It may not be possible to solve the technical problem of the present invention either by the volume fraction of the reinforcing filler not present, or by the content and volume fraction of the reinforcing filler not according to the present invention. Demonstrate.

  Six sidewall compositions A, B, C, D, E and F were prepared according to the method described in detail in the previous section. These compositions described in Table 1 below (each amount expressed in phr) differ in the nature and content of the reinforcing filler and also in the volume fraction of the reinforcing filler.

Therefore, compositions A, B, C, D, E and F are defined as follows:
Control composition A, commonly used as a side wall for passenger cars, contains 50 phr of carbon black with a BET specific surface area equal to 39 m ² / g, with a reinforcing filler volume fraction equal to 15.5%.
Composition B according to the invention comprises 28 phr carbon black with a BET specific surface area equal to 62 m ² / g, with a reinforcing filler volume fraction equal to 9.2%.
Composition C according to the invention comprises 25 phr carbon black with a BET specific surface area equal to 62 m ² / g, with a reinforcing filler volume fraction equal to 9.1%.
Composition D according to the invention has a BET specific surface area equal to 64 m ² / g and a reinforcing filler volume fraction equal to 9.1% of a 25 phr carbon black mixture consisting of 60% N347 and 40% N683. Including.
- The content of the reinforcing filler and not according to the invention by the volume fraction Composition E, 62m ² / g to equal a BET specific equal reinforcing filler volume fraction in 15.2% of carbon black 43phr having a surface area Including.
-Also according to the content of reinforcing filler, composition F not in accordance with the invention comprises 43 phr carbon black with a BET specific surface area equal to 62 m ² / g in a reinforcing filler volume fraction equal to 12.4%. Including.

Composition D according to the invention consists of Composition C and the reinforcing filler of Composition D consisting of 60% N347 and 40% N683, a BET specific surface area of 64 m ² / g and a COAN oil absorption of 93 ml / 100 g Note that the carbon black mixture is characteristic in value. These BET and COAN values were measured under the same measurement conditions as in the carbon black used in composition C.

(1) 天然ゴム；
(2) 96％(モル%)のシスを含むLanxess社からのポリブタジエンCB 24；
(3) カーボンブラック N683 (39m²/gに等しいBET；COAN：89ml/100g)；
(4) Sid Richardson社からのカーボンブラック SR401 (BET：62m²/g；COAN：107ml/100g)；
(5) 60%のN347 (BET：88m²/g；COAN：98ml/100g)と40％のN683の混合物；
(6) MESオイル(Flexon 683；Exxon Mobil社)；
(7) N‐1,3‐ジメチルブチル‐N'‐フェニル‐パラ‐フェニレンジアミン(6‐PPD)；
(8) N‐シクロヘキシル‐2‐ベンゾチアジルスルフェンアミド(Flexsys社からのSantocure CBS)。 Table 1

(1) Natural rubber;
(2) Polybutadiene CB 24 from Lanxess with 96% (mol%) cis;
(3) Carbon black N683 (BET equal to 39m ² / g; COAN: 89ml / 100g);
(4) Carbon black SR401 from Sid Richardson (BET: 62m ² / g; COAN: 107ml / 100g);
(5) Mixture of 60% N347 (BET: 88m ² / g; COAN: 98ml / 100g) and 40% N683;
(6) MES oil (Flexon 683; Exxon Mobil);
(7) N-1,3-dimethylbutyl-N'-phenyl-para-phenylenediamine (6-PPD);
(8) N-cyclohexyl-2-benzothiazylsulfenamide (Santocure CBS from Flexsys).

The dynamic characteristics of these compositions A, B, C, D, E and F were measured to determine the rolling resistance performance. The rolling resistance performance results are shown in Table 2 below.

Table 2

  Only compositions B, C and D according to the invention have an improved rolling resistance index compared to control composition A. Compositions E and F differ from B and C by the volume fraction and content of reinforcing fillers not in accordance with the present invention and have a worse hysteresis compared to the control; Compared to the control, it means a higher rolling resistance of the side walls containing compositions E and F. Therefore, these compositions E and F that adversely affect rolling resistance are intended to improve the side wall carving resistance without affecting the good crack resistance performance and low rolling resistance performance. The technical problem could not be met and was therefore not evaluated for side wall carving and crack resistance.

Thus, compositions A, B, C and D were used to form tire sidewalls having dimensions 205 / 55R16; each sidewall is formed from a single portion ranging from the bead to the tread contact point. These tires are identical except for the composition that constitutes the sidewall of each tire. Each tire with dimensions 205 / 55R16 was tested under nominal (pressure, load, rim) conditions as defined by the ETRTO standard.
Table 3 below shows the carving resistance performance and crack resistance performance of the side walls FA, FB, FC and FD containing the compositions A, B, C and D, respectively.

Table 3

Surprisingly, carbon black according to the present invention, ie having a BET specific surface area equal to 62 m ² / g (at 28 phr and 25 phr for the respective reinforcing filler volume fractions of 9.2% and 9.1%), respectively. The included sidewalls FB and FC have been observed to have a higher carving resistance index than the control sidewall FA. These results relate to the prior art that the person skilled in the art knows that reducing the content and volume fraction of reinforcing filler has the consequence of degrading the wear resistance performance, in particular the carving resistance performance. That is especially unexpected.

  Furthermore, the improvement with respect to crack performance is very substantial in either the sidewall FB or the sidewall FC according to the invention, in particular in the sidewall FB which does not have any propagation of the initial cut under the test conditions.

Also, the sidewall FD according to the present invention comprising a carbon black mixture having a specific surface area equal to 64 m ² / g also has a higher carving resistance than the control sidewall FA, with a crack resistance value at least as high as that of the control FA. It has also been observed.

Recall that the reinforcing filler of composition D is actually a mixture of carbon black consisting of 10 phr N347 and 15 phr N683. Thus, this performance compromise is especially the carbon black mixture with a specific surface area between 50 m ² / g and 69 m ² / g (other characteristics of the composition, in particular the volume fraction and inclusion of reinforcing fillers) by) the extent that is also followed amount, it has been achieved even if each of the specific surface area of each of the carbon black in the mixture is outside the range according to the present invention in the range of 50m ² / g~69m ² / g Is noted.

  In short, a substantial improvement in the carving performance of the tire according to the present invention has been achieved without sacrificing rolling resistance performance or crack performance. The substantial improvement in the carving performance is even accompanied by a strong improvement in rolling resistance and a strong improvement in crack resistance under certain reinforcing filler content and volume fraction conditions; This is completely unexpected.

Claims (19)

A tire sidewall comprising at least part of a rubber composition based on at least a diene elastomer, a crosslinking system and a reinforcing filler, wherein the reinforcing filler content in the composition is 20 to 40 phr (elastomer The volume fraction of the reinforcing filler in the composition is in the range of 8.0% to 13.0%, and the reinforcing filler is mainly carbon black or carbon. It comprises a mixture of black, the tire sidewall in which the BET specific surface area lies in the range of 50m ² / g~69m ² / g. 50m ² / g~69m the carbon black or carbon black mixtures having a BET specific surface area in the range of ² / g is at least 85 wt% of the reinforcing filler, more preferably at least 95 weight of the reinforcing filler The tire side wall according to claim 1, which constitutes%. ^{2. The} carbon black or carbon black mixture having a BET specific surface area in the range of 50 m < ² > / g to 69 m < ² > / g is used as a mixture with one or more other organic or inorganic reinforcing fillers. Or the tire side wall of 2. The carbon black or carbon black mixtures having a BET specific surface area in the range of 50m ² / g~69m ² / g constitutes 100% of the reinforcing filler, according to claim 1 or 2 tire sidewall according. The carbon black or carbon black mixtures having a BET specific surface area in the range of 50m ² / g~69m ² / g has a COAN oil absorption in the range of 80ml / 100g~120ml / 100g, of claims 1 to 4 The tire side wall according to claim 1.   The tire sidewall according to any one of claims 1 to 5, wherein the proportion of reinforcing filler in the composition varies from 20 phr to 35 phr.   The tire sidewall according to claim 6, wherein the proportion of reinforcing filler in the composition varies between 25 phr and 30 phr.   The tire sidewall according to any one of claims 6 and 7, wherein the volume fraction of the reinforcing filler in the composition varies between 8.0% and 10.0%.   The tire sidewall according to claim 8, wherein the volume fraction of reinforcing filler in the composition varies between 8.7% and 9.4%.   30 to 55% natural rubber, synthetic polyisoprene or a mixture of natural rubber and synthetic polyisoprene, and 45 to 70% polybutadiene, styrene / butadiene copolymer, isoprene / butadiene copolymer, isoprene / styrene copolymer. Tire sidewalls according to any one of the preceding claims, comprising an elastomer mixture comprising and a diene elastomer selected from isoprene / butadiene / styrene terpolymers and mixtures thereof.   The tire sidewall according to claim 10, wherein the diene elastomer is polybutadiene, preferably cis-1,4-polybutadiene.   The tire sidewall according to any one of claims 1 to 11, wherein the rubber composition contains a plasticizer.   The tire side wall according to any one of claims 1 to 12, wherein the portion of the side wall is placed on an outer surface of the side wall.   The tire sidewall according to any one of claims 1 to 13, wherein the portion of the sidewall extends from the crown to the bead.   The tire containing the tire side wall of any one of Claims 1-14. A tire sidewall composition based on at least a diene elastomer, a crosslinking system and a reinforcing filler, wherein the reinforcing filler content in the composition varies between 20 and 40 phr, and the reinforcement in the composition the volume fraction of the use filler is in the range of 8.0% to 13.0%, and the reinforcing filler is mainly carbon black or having a BET specific surface area in the range of 50m ² / g~69m ² / g A method for producing a tire sidewall composition comprising a mixture of carbon black, comprising the following steps:
Kneading the diene elastomer and the reinforcing filler thermomechanically until a maximum temperature between 110 ° C. and 190 ° C. is reached;
Cooling the mixture to a temperature below 100 ° C .;
-Thereafter, the step of incorporating the crosslinking system;
-Kneading everything until a maximum temperature lower than 110 ° C is reached to obtain a rubber composition;
A step of calendering or extruding the rubber composition. 50m ² / g~69m the carbon black or carbon black mixtures having a BET specific surface area in the range of ² / g is at least 85 wt% of the reinforcing filler, preferably at least 95 wt% of the reinforcing filler The manufacturing method according to claim 16, further preferably comprising 100%.   18. A process according to claim 16 or 17, wherein the proportion of reinforcing filler in the composition varies from 20 phr to 35 phr, preferably from 25 phr to 30 phr.   19. A process according to claim 18, wherein the volume fraction of reinforcing filler in the composition varies between 8.0% and 10.0%, preferably between 8.7% and 9.4%.